The problems, to the solution of which the present invention is directed, are best understood by reference to a specific example.
In one method of harvesting trees, a tree feller moves through an area felling and limbing trees selected for cutting. A diesel-powered log-skidder, equipped with a winch, is utilized to collect together several of the logs produced by the felling operation using the winch cable and choker cables to drag the logs towards the skidder, which then skids the entire bundle of collected logs out to a "landing" for subsequent collection and trucking to a sawmill.
Operation of such a log-skidder requires that the operator position the vehicle within a winch cable length of the logs to be collected. The operator then releases a drum brake on the winch, descends from the vehicle and carries a choker cable towards a first log, whilst dragging the winch cable from the drum. Having positioned the choker cable around the log and attached the winch cable, the operator must then return to the machine, manipulate a control to start the winch and drag the log to a selected bundling position, and stop the winch. This sequence must be repeated for each of the logs to be collected and for the application of a choker cable to the completed bundle prior to towing it to the landing.
The physical exertion involved for the skidder operator is considerable. The floor of the cab of a typical skidder is about 5 feet above ground level which necessitates a vertical climb and descent via precarious handholds and steps. A bundle of five logs will necessitate at least six round-trips between logs and vehicle, and possibly more since choker cables sometimes slip off logs and must therefore be reset. This is an energy and time consuming task, especially in adverse weather conditions such as deep snow. The rigour of the task can be alleviated by using a crew of two, but this is obviously an expensive solution to the problem.
A system of remote control which permits the operator to exercise all the functions of the winch (brake release, apply brake and rewind) without returning to and mounting the vehicle is obviously highly desirable so as to save the necessity for a second operator, or to save time and physical exertion on the part of a single operator.
Use has been made of relatively conventional radio remote control equipment with a view to overcoming the problems outlined above. However, conventional radio control equipment is not ideal for the purpose. Conventional transmitter units, although they can be quite small in size, are nevertheless an additional encumbrance for the operator, and since the transmitter must be housed in a readily accessible position, it is also very vulnerable to accidental damage and in particular to accidental transmission of control signals under inevitably rough conditions of usage. Moreover, it is difficult for an operator wearing the heavy gloves necessary for the job to operate the controls of such a transmitter. Unfortunately, the more compact the transmitter, the more difficult the controls are likely to become to manipulate.
The present invention is directed toward providing a remote control transmitter which eliminates the need for manipulating controls in order to transmit the several different required signals, which is not cumbersome to carry, and which much reduces the possibility of accidental damage or transmission.
The invention also seeks to alleviate certain other problems which have become apparent with prior art remote control transmitter apparatus. Firstly, it is common for a number of log skidders to be operating in the same area. It is therefore of great importance that the receiver on a particular skidder should respond only to the transmitter of its operator, because of the risk of accidents that would otherwise arise. Secondly, it is important to secure reliable transmission over a sufficient distance to ensure reliable reception, regardless of the position or attitude of the operator, who will often not be facing the receiver when he operates the transmitter. With a conventional transmitter, operated in front of the body, this means that the user's body is interposed between the transmitter and the receiver. Whilst this may not itself cause sufficient attenuation of the transmitted signal to prejudice the reliability of reception, the user's body may interact with the transmitter antenna in such a manner as to cause nulls in the radiation pattern of the transmitter. Moreover, even without interaction with the body of the user, the antenna may have nulls in its radiation pattern, and it is difficult to ensure that the transmitter is never held so that the receiver lies in such a null.